A portable terminal apparatus such as a portable terminal device typically includes a first housing (fixed plate) having ten-keys or the like provided thereto, and a second housing (moving plate) having a liquid crystal display device provided thereto and being openable and closable relative to the first housing. As for typical structures for opening and closing the second housing relative to the first housing, there is a type which opens and closes by connecting the first and the second housings with a hinge mechanism and rotating the second housing relative to the first housing (collapsible type) and a type which opens and closes by sliding the second housing relative to the first housing (slidable type).
Meanwhile, in recent years, portable terminal devices are being provided with more functions, devices capable of receiving digital terrestrial broadcast are being provided, and the size of liquid crystal display devices are becoming larger. Along with the providing of more functions, the number of keys on a keyboard for performing an input process on the portable terminal device is increasing. Therefore, the size of the keyboard tends to become larger. Although improvement of portability of the portable terminal device is being demanded constantly, there is a limit in increasing the size of the liquid crystal display device or the keyboard.
In a state where the collapsible type portable terminal device is in a collapsed state, its liquid crystal display device becomes hidden. This leads to a problem where the liquid crystal display device cannot be used in the collapsed state. Although the problem of the collapsible type portable terminal device does not occur in the slidable type portable terminal device, generation of an overlapped portion between the first and the second housings is unavoidable when in an open state. This leads to a problem of being unable to utilize space efficiently.
Accordingly, there is proposed an opening/closing device having first and second housing that become flat (being on the same plane) when the first and the second housings are in an open state (see Patent Document 1-3). With this configuration, the liquid crystal display device can be used even when the first and the second housings are in a closed state. In addition, there is no overlapped part between the housings, and space can be efficiently utilized in a state where the first and the second housings are in an open state.